The West Nile Virus: A cause for local concern?

The West Nile virus was first detected in the United States in 1999, and in Pennsylvania a year later.

By Richard L. Gaw

Staff Writer

The Pennsylvania West Nile Virus Control Program has conducted 346
mosquito samples in Chester County this year, and of them, 116 have
been tested for presence of the virus. Of those, four have tested
positive, and on July 10, the Chester County Health Department sent
out a written statement saying that the presence of the West Nile
Virus had been detected in West Goshen Township.

On July 16, a mosquito sample tested positive for West Nile Virus
in Downingtown Borough. The virus has also been detected in mosquito
samples collected in Easttown, Treddyffrint and Uwchlan Counties this
year, as well as in Berks, Montgomery, Philadelphia and Bucks
Counties. This year alone, the program has verified that 64 positive
samples of the virus have been detected in nearly half of
Pennsylvania's 67 counties.

As the calendar begins its slide into the lazy, hazy days of
August and September, and as the waft of backyard barbecues and
chlorinated pools drifts into Chester County's days and nights, are
individuals and families relegated to fearing that their summer will
be impeded by virus-carrying mosquitoes? In other words, is there
reason to worry?

Not really,
authorities are saying.

"The
detections throughout Chester County of the West Nile Virus (WNV) are
not a cause for major concern, as these detections are fairly
standard for this area and this time of year," said Jeanne E.
Casner, County Health Director for the Chester County Health
Department [CCHD]. "As context, there were 61 and 142 positive
mosquito samples in 2012 and 2013, respectively. There are
fluctuations from year to year; however, this year is average."

The
chance of contracting West Nile Virus from an infected mosquito is
small and chances of becoming seriously ill are even smaller. Most
people bitten by a mosquito carrying the virus aren't in danger,
given that the virus can only be transported to humans when a
mosquito's salivary gland reaches the person's blood. Even then,
three in four people fight off the virus. Only one in 150 people who
become infected with the West Nile virus develop a severe illness
with reports of high fever, confusion, severe headache, and stiff
neck. When symptoms do occur, they start three to 15 days after the
mosquito bite.

The West Nile virus, first discovered in Uganda in 1937, has since
spread to many parts of the world and was first detected in the
United States in 1999, and in Pennsylvania a year later.
The United States is in the midst of the largest outbreak of
West Nile Virus since 1999, the Center for Disease Control announced
recently. So far this year, more than 1,100 cases of human West Nile
infection have been reported, about half of them in Texas, and all
told, about 40 people have died from the virus. More cases are
expected, since West Nile virus infections generally peak in late
August and September.

Close
to home, Chester County had one confirmed human case in 2012, the
first since 2008. In 2012, 146 Mosquito samples tested positive for
West Nile Virus in Chester County, compared to 29 positive samples in
2011.

Experts can only speculate about the reasons for this dramatic
increase in cases, but it likely has some relation to the record warm
temperatures this past winter and spring, followed by a very hot
early summer. The breeding cycles of mosquitoes speed up in hotter
weather, and the virus seems to replicate faster in warmer
temperatures.

And then
there are humans. "Human influence, such as leaving tire piles
or unmaintained swimming pools, can create breeding grounds that also
have a direct impact on the numbers we see, particularly in more
suburban and urban areas," Casner said.

The CCHD recommends that individuals take personal
precautions to minimize the possibility of being bitten by infected
mosquitoes. This includes staying indoors at dawn or dusk when
mosquitoes are most active, wearing long sleeve shirts and long pants
when outside and using insect repellents when mosquitoes are active.
The heightened concern will probably remain until the first frost
which usually occurs in mid-October.

The CCHD is working with
property owners to eliminate breeding sources, which include standing
water, such as tires, pools, buckets and other artificial containers.
County regulations prohibit property from being maintained in a
condition conducive to the breeding of mosquitoes, and citations may
be issued for failure to comply with these regulations. To help stem
the flow of mosquito larvae, biological larvicide is used to treat
areas of stagnant water that cannot be drained. Larvacide controls
mosquitoes in the larval form and is an environmentally safe method
of mosquito control.

"It
is the individual home or business owner's responsibility to
maintain their property in a manner that is not conducive to mosquito
breeding," Casner said. "The county steps in when someone
is not maintaining their property, and when necessary enforcement
action is warranted in conjunction with our county nuisance
regulations."

Casner
said that the department's duties relate to education, surveillance
and early treatment, such as applying larvacide. CCHD engages staff
with these duties as a first resort. Surveillance involves setting
traps in which mosquitoes are caught, counted and samples are tested
for WNV. As a last resort when all other measures are no longer
effective, CCHD staff will engage in other duties such as adult spray
treatments.

"While
education and information sharing are critical elements to CCHD’s
WNV program, the program also includes setting traps in which
mosquitoes are caught, counted and samples submitted for testing,"
Casner said. "In addition, CCHD staff are involved in spraying
to eliminate mosquitoes based upon the results of the trappings and
tests."

For more information on the West Nile Virus in
Chester County, visit www.chesco.org/wnv
or call 610-344-6752.

West
Nile Virus Precautions

Residents
are encouraged to take the following precautions to reduce mosquito
breeding on their property:

 Dispose
of open containers that may collect water, such as tin cans, plastic
containers, ceramic pots, etc.

 Drill
holes in the bottom of outdoor recycling containers so that water
will not collect.

 Keep
your property clear of old tires.

 Clean
roof gutters, particularly if leaves from surrounding trees have a
tendency to plug drains.

 Turn
over plastic wading pools when not in use.

 Turn
over wheelbarrows and don’t let water stagnate in birdbaths.

 Aerate
ornamental pools or stock them with fish.

 Clean
and chlorinate swimming pools when not in use. A swimming pool left
untended by a family on vacation for a month can produce enough
mosquitoes to result in neighborhood-wide complaints. Mosquitoes may
even breed in the water that collects on pool covers.

 For
stagnant pools of water that cannot be removed or drained, homeowners
can buy BTI products such as mosquito dunks, which are available at
lawn/garden, outdoor supply and home improvement stores. This
naturally occurring bacterial product kills mosquito larvae but is
safe for people, pets, aquatic life and plants.

Source: Chester County Health Department

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